How is it different ? From the perspective of the companies, it is in their interest for the prospective employee to bid to fill position.

I see. So we should start listing benefits to doing our job for a plumber?

"Hey there Plumber, if you do this job, I'll give you health insurance for the two days it takes you to do this job. I'll provide a gym membership, free coffee, and pay your taxes"

Its called analogy, not everything has to be the same.

In the case of plumber, the benefits for plumber to take the job is they get to make money.

I'm saying the analogy in this case, doesn't work. Hiring a plumber, carpenter, electrician on a per job basis is not the same as hiring an employee (hopefully for a long-term commitment).

We are specifically talking about the case of hiding salary right ? How is it different ?

It is different that plumbing/carpenting et al are one time gigs. They just walk away collecting their money once they put in their fixed hours. You will not be able to call your plumber at midnight if you feel like some thing that needs to be fixed.

Your analogy might work for short term contractors but not for a full time employment, where essentially you are putting yourself at your employers service virtually 24/7 with almost no extra pay while doing intangible (aka knowledge) work where the employer might get 5x or 200x return out of your work, but essentially you will just get almost linear pay raises (even including performance bonuses).

You cannot compare a full time knowledge worker with a gig worker that does tangible physical work.

Plumber's job with a single customer usually lasts one or two days, so the plumber's income is not dependent on any single customer. They might be willing to risk it and take a job without a price set beforehand, because the worst case scenario they lose, say, a single day pay.

Also, a good approach from the employee side is to explain during the interview what all they can do for the company. That's the approach I took last time around, I got in the mindset that I was a consultant that was there to solve their problems, and this is how. Got the job offer an hour later.

Kind of like a plumber saying "We don't need to dig up your front yard and charge 9 grand, for 500 bucks we can robotically patch the pipe from the inside".